Conventional gas burning barbecues are constructed with a grill on which food is supported, beneath which a burner is positioned. Between the burner and the grill is a layer of lava or other type of porous rock which absorbs grease and other drippings from meat being cooked on the grill. The burner is usually formed from a pair of hollow tubes of "U"-configuration joined at their bases to form an "H"-configuration. Fuel from a portable fuel tank associated with the barbecue is supplied to the burner tubes through a pair of valve-controlled gas outlet tubes, so that gas may be provided to either half or simultaneously to both halves of the burner. Each of the hollow burner tubes is provided with an air/gas intake tube located adjacent its inlet end, and a venturi in the intake tube spaced from the inlet end to draw a predetermined amount of air through an opening in that intake tube to mix with the gas to provide a proper combustion mixture of gas and air. Thus, one of the air/gas intake tubes is associated with a different one of each of the burner tubes to provide independent control of the air and gas mixture being provided to its corresponding half of the burner.
One of the problems presented with such a construction of burner is that it is extremely difficult to provide a cooler temperature in the center of the barbecue, for example as would be desirable when meat is being cooked on a rotisserie centered in the barbecue. While shutting off the flow of gas and air to one half of the "H"-configuration of the burner will cool that half, this does not permit cooling of the center of the barbecue. Thus, items with high fat content or items intended to be cooked using a rotisserie which must be cooked with a minimum of flare-up, can only be cooked with difficulty.
Of background interest is Lohmeyer et al U.S. Pat. No. 4,677,964 issued Jul. 7, 1987 which describes and illustrates a gas burning barbecue in which three linear tubes are positioned spaced from side-to-side below the grill in a barbecue, each of the burner tubes having associated with it an independent gas outlet tube controlled by a different gas feed valve.
Other barbecue patents of general background interest include Steven et al U.S. Pat. No. 4,727,853, issued Mar. 1, 1988 and Schlosser et al U.S. Pat. No. 4,829,978 issued May 16, 1989.
Also of background interest is a charcoal grill conversion apparatus described and illustrated in Swanson et al U.S. Pat. No. 3,824,984 issued Jul. 23, 1974 in which a pair of gas burner tubes, of circular configuration, one of greater diameter than the other, are concentrically positioned with respect to each other and centered within a standard charcoal grill. A gas outlet tube with a single gas feed valve simultaneously feeds gas and air to the two burner tubes. No independent control of the burner tubes is taught.
It is an object of the present invention to provide a burner for conventional gas burning barbecues which will permit direct or indirect heating to both central and outlying parts of the barbecue beneath the grill. It is a further object of the present invention to provide such a burner which can be retrofitted into gas burning barbecues to replace conventional "H"-configuration burners.